AlfaTech Big Book: Mission Critical

M I S S I O N C R I T I C A L

Temperature Control : The philosophy of controlling temperature in the data center has been driven by data center operator concerns and desires to manage this function. A sophisticated operator may desire zone temperature control based on loading of given areas of the data floor; this may include modulation of air volume (savings on fan power usage) and or modulation of air temperature, but usually not both because of control cost. Some of our clients desire a design using hot and cold aisles between alternating rows of server racks; however this brings the problem of short circuiting of hot air into cold aisles on ends and at top of racks. If server cabinets are used, the specifics of the cabinets will effect the air delivery method and temperature control selected. The need for redundancy and reliability has led many data center operators to utilize PLC based controls over DDC based controls. AlfaTech has extensive experience providing detailed design of both systems types. Humidity Control : The philosophy of humidity control in the data center is driven by two parameters: range of operation and speed of control response. Range is usually between a low of 25% to 35% RH and a high between 65% and 80% RH; the lower the low, and higher the high, the easier the control and less expensive the operation. Speed of response will dictate the type of system required, the faster the control, the higher the cost, and the more energy used. Fast response is normally not a factor unless the user is unaware of the implications; servers do not care what the humidity is as long as it is below 80% to reduce corrosion and above 25% to reduce static charge potential for dissipation.

Fire Protection : Is the client standard a VESDA detection system? Does the client desire an FM-200 system as a standard? It is assumed that a zoned preaction dry pipe distribution system will be used to feed fire sprinkler heads. Fuel Oil : Design philosophy is based on rate of use, timing for deliveries, and length of time the data center must remain functional. Other design considerations are actual capacity that can be extracted from tankage, fuel filtration requirements, and redundancy of fuel delivery system to generators. Calculations and Diagrams: Alfa Tech’s design philosophy is to diagram systems for purpose of discussion and to provide options to allow the owner to make educated decisions on systems they want implemented in their data center facility. Initial calculation spreadsheets are set up to allow us to easily modify inputs to perform what-if system variations. During this phase of development, we like to identify cost and schedule implications to eliminate non-feasible solutions. AlfaTech is experienced in data center commissioning and understands the problems to include sequencing to failure and assuring system design allows this failure to occur. Maintenance : One of the key elements in designing a data center is the ability to allow maintenance of equipment to take place without effecting operating systems. Maintenance can be very difficult in a minimally designed system, therefore install dollars must be expended to ensure the ability to take equipment off line.

HVAC Systems : The philosophy of design for the data center cooling systems is primarily dependent on three things: local codes; the physical restraints and opportunities of the facilities such as ability to place equipment in exterior yard or on roof; and the preferences of the data center operator. AlfaTech designs have included: on floor CRAC units with DX cooling in yards and on roofs; CRAC units with chilled water cooling using both air cooled chillers and dry coolers located in yards and on roofs; rooftop air cooled package air handling units serving air through duct down to under floor; interior mezzanine located air handlers with ducted air down to floor; rooftop air cooled chillers to provide cooling; and floor mounted built up air handlers supplying air under floor. The ideal power efficient system will incorporate air side economizers to use free cooling and/or wet side economizers such as dry coolers. Wet towers and other evaporative based cooling solutions are a problem due to the necessity of storing large quantities of water. If a large source of water is available, such as a lake or ground water wells, this is a plausible option. Air discharge pattern to underfloor or into cabinets can present design problems if improperly implemented, as the venturi effect can pull air from the data room back under the raised floor.